add memory usage module with collector, scene, and script

panels/memory/memory_collector.gd

@@ -0,0 +1,36 @@
+extends RefCounted
+class_name MemoryCollector
+
+
+func collect() -> float:
+	var meminfo := _read_meminfo()
+	if meminfo.is_empty():
+		return 0.0
+
+	var total := meminfo.get("MemTotal", 0)
+	var available := meminfo.get("MemAvailable", 0)
+
+	if total == 0:
+		return 0.0
+
+	return 100.0 * (1.0 - float(available) / float(total))
+
+
+func _read_meminfo() -> Dictionary:
+	var file := FileAccess.open("/proc/meminfo", FileAccess.READ)
+	if file == null:
+		return {}
+
+	var result: Dictionary = {}
+	while not file.eof_reached():
+		var line: String = file.get_line().strip_edges()
+		if line.is_empty():
+			continue
+		var parts := line.split(":", false)
+		if parts.size() < 2:
+			continue
+		var key := parts[0].strip_edges()
+		var val_str := parts[1].strip_edges().split(" ", false)[0]
+		result[key] = val_str.to_int()
+
+	return result